ByAlexander Reshetnikov and Gennady Novik, ReutersMarch 20, 2016

Russian Police and Emergency Ministry employees investigate the wreckage of a crashed plane at the Rostov-on-Don airport, about 950 kilometers (600 miles) south of Moscow, Russia, Sunday, March 20, 2016. Winds were gusting before dawn Saturday over the airport in the southern Russian city of Rostov-on-Don when a plane carrying 62 people from a favorite Russian holiday destination decided to abort its landing.

ROSTOV-ON-DON, Russia — Relatives gathered to mourn the 62 victims of a passenger jet crash in southern Russia on Sunday and officials warned an investigation could take weeks to determine the cause of the downing.

At Rostov-on-Don airport about 400 people paid their respects to the 55 passengers and seven crew who died when the Boeing 737-800, operated by Dubai-based budget carrier Flydubai, crashed in the early hours of Saturday.

Bereaved relatives laid red and white carnations on a growing pile of flowers, candles and children's toys, framed by photos of the dead. "We mourn," read an inscription listing the victims' names.

"The whole world is expressing its condolences to us. But it is impossible to forget this."

At the crash site, Russian workers finished their search of the snow-covered wreckage, having sifted more than 200 pieces of the victims' bodies scattered across the airfield, Russian TV reported.

Russia's airline regulator said work had started extracting information from the doomed plane's flight recorders, which were badly damaged in the crash.

"The received recorders are badly damaged mechanically," Russia's Interstate Aviation Committee (IAC) said in a statement on its website, alongside a photo of a crumpled recorder.

"Specialists ... have started the inspection, opening and removing the memory modules from their protective coverings for further work to restore the cable connections and prepare to copy the data," the IAC said.

RIA news agency cited an IAC official as saying it could take one month to decode information from the recorders.

STRONG WINDS

Under international aviation rules, the investigation will be led by Russia's air safety investigation agency with representatives from the United States, where the jet was made, and the United Arab Emirates, where the airline is based.

Flydubai's CEO Ghaith al-Ghaith said on Saturday it was too early to determine the cause of the crash, but officials have suggested it could have been caused by pilot error, a technical problem or strong winds at the airport.

Speaking at a news conference in Dubai on Sunday he said: "We have high confidence in the Russian authorities who are capable of managing local conditions for flights," he said. "We fully trust the Russian authorities in this."

"The airport was open. It was good enough to operate and good enough to land, as per the authorities," he added. "The weather conditions were good enough for the flight."

Flydubai said in a statement it was organizing hardship payments to families of the victims amounting to $20,000 per passenger, in accordance with its conditions of carriage.

The airline has not canceled or delayed any flights because of the crash, it added, and Russian Transport Minister Maxim Sokolov said the airport would reopen on Monday morning.

Security services in the Middle East and Russia are on heightened alert for militant threats to aviation following the Islamic State claim of responsibility for downing a Russian passenger plane over Egypt's Sinai Peninsula in late October. (Additional reporting by Sylvia Westall in Dubai; Writing by Jack Stubbs; Editing by Stephen Powell)